The compositions of the present invention relate to a detergent composition comprising a quaternary ammonium salt detergent and optionally an oxygen-containing detergent in combination with an active metal containing compound, such as a fuel catalyst and/or an exhaust trap additive. These compositions may be used in fuels and provide improved engine performance when such fuels are used, specifically by reducing fuel injector fouling in the engine and/or by improving the regeneration of the particulate exhaust trap.
It is well known that deposits can form in the injectors of diesel engines during use. The amount of deposits and rate of formation depend on the fuel being used in the engine as well as the additives present in that fuel. Fuels which contain unstable components, such as fatty acid methyl esters (FAME), tend to form more deposits than mineral-based fuels that do not contain such components.
In addition, the presence of metals in fuels, such as metal-containing fuel catalyst, can lead to higher levels of deposits and so higher levels of injector fouling.
Metals may be introduced into fuels from various sources including contact with metal components in the fuel distribution system, contamination, and by other means. One example of the presence of a metal in a fuel is through the deliberate addition to the fuel of a metal catalyst. Such catalysts can aid in Diesel Particulate Filter (DPF) regeneration and so are desirable, although the deposits they may promote are not. DPFs are often used on the exhausts of diesel vehicles to filter out soot from the exhaust gas. The filter quickly becomes filled with soot, and requires regular cleaning. This is done by raising the exhaust temperature to cause the soot on the filter to burn off. This process is facilitated by adding a metal catalyst to the diesel fuel. The catalyst becomes incorporated in the soot, and allows the soot to be burnt at lower temperatures. The kinetics of the combustion is also improved. A preferred method of delivering such catalysts is by continuously dosing a metal-containing additive into the fuel from an on-board container. The additive then passes through the engine and into the exhaust system where it comes into contact with the DPF and the soot on the DPF. Unfortunately, such metal-containing additives can promote engine deposit formation, leading to higher levels of injector fouling in the engine.
Deposits can lead to loss of engine performance and eventually, to possible damage of the engine. It is known that detergent additives can be used to reduce or eliminate deposit formation in injectors. However, particularly in the case of fuel-borne DPF catalysts, there is continued need for providing compositions that allow for use of effective DPF catalysts and other metal-containing additives while controlling injector fouling and other engine deposit-related problems, while doing so with the least amount of additive, and so the least cost, possible.
Among the fuel-borne catalysts (FBC), dispersions of rare earth or iron compositions are known as efficient additives for the DPF regeneration. These colloidal dispersions must have good dispersibility in the medium into which they are introduced, high stability over time and sufficient catalytic activity. Known colloidal dispersions do not always satisfy all of those criteria. They may, for example, have good dispersibility but not sufficient stability especially in some types of fuel such as biofuels. Furthermore, as mentioned above, the dispersions must lead to a limited injector fouling. More-over, the presence of a fuel-borne catalyst in the fuel may decrease the oxidation resistance of said fuel, more particularly in the case of biofuels.
There is a need for providing compositions comprising a dispersion of active additives for the DPF regeneration with good stability, limited injector fouling or which induces a limited decrease of the oxidation resistance of the fuel.